Measurement of the stresses and component deformations occurring during the operation of a wind turbine generally takes place using measuring devices, which are part of at least one transmitting/receiving device, and reflector devices arranged remotely from the transmitting/receiving device. The transmitting device sends signals to a reflector which are reflected and sent to the receiving device similarly arranged remotely from the reflector. In the receiver the reflected signals are evaluated and if necessary converted into measured values via a computing unit.
The measuring device may, for example, be what is referred to as a contactless remote measuring device in the form of a laser, a camera or similar arrangements.
The signals may be optical, sonar, laser or electromagnetic signals. The reflector is usually what is known as a retroreflector, arranged symmetrically about the respective axis at the installation point in the wind turbine, for example, the blade axis in a rotor blade or the tower axis in the tower.
The wind turbine unit may, by way of example, be a rotor with its protruding rotor blades, a nacelle—also referred to as a gondola—that is stationary relative to the rotor, or the turbine tower, at the top of which the gondola is mounted so that it can rotate relative to the tower. The measuring device can be arranged in an elongated cavity of the abovementioned component.
The spatial displacements of markings on the reflector surface caused by the aerodynamic loads can thus be detected and quantified by the measuring device.
For the precise determination of the aerodynamic loads, prior to the actual measurement, precise alignment and adjustment of an alignment face of the measuring device between the transmitting/receiving device and the reflector is required, in order to avoid influences of the measuring point and measuring range. The aim is that the useful measuring range in the measuring device corresponds to the deformations at the measuring point. The measuring device is therefore arranged in a bracket, secured on opposing sides in the cavity and having adjusting devices for accurate adjustment and alignment of the alignment face relative to the bracket. The bracket has to be adjustable to allow for adjustment of the measuring device during installation. Once alignment and adjustment are complete, the measuring device remains fixed relative to the alignment face of the associated reflector. All subsequent movements of the reflector are thus the result of the deformations resulting from the aerodynamic loads on the wind turbine component, which are to be measured.
EP 2 453 136 A shows an alignment and adjustment device for a measuring device in a cavity in a rotor of a wind turbine for measuring deformations, in particular of a rotor blade arranged on the rotor. The transmitting/receiving device of the measuring device is located in a housing, secured to a bracket in the cavity of the rotor, wherein the bracket takes the form of a distance plate with interspace supported at three points. Adjustment for each bearing position is via adjustable fixing bolts with the interpositioning of a compression spring. A lock screw sits in an additional screw hole of the distance plate and, following adjustment of the housing, is brought into contact with an alignment face, opposite the distance plate with interspace.
The disadvantage of the adjustment and alignment described above is that the adjustment of the bolts has to be performed separately for each bearing point and then precise positioning via the lock screw is required. Furthermore, the at least three bearing points must be arranged tangentially to one another. The adjustment and alignment of the measuring device is therefore fairly time-consuming and can lead to inaccuracies, so that measurement results based on such adjustment and alignment may be inaccurate or falsified.
DE 1785791 U discloses a tripod holder for a recording camera with a tripod head adjustable in various directions and an adjustable friction brake, the brake block of which can be applied by means of a rotatable cam disc.